North American Impacts of El Nino Jon M Schrage

r(-SOI 3mrm,OLR’), r(-SOI 3mrm,  r(-SOI 200)

Rossby Wave Source Conservation of Absolute Vorticity The twin anticyclones aloft are what initially displaces the air parcels. Results in a pattern of troughs and ridges far downstream.

PNA PATTERN

The following slides are composites from January

500mb heights

1000mb T

OLR

Precip

Sea Level Pressure

Changnon What counted as an impact of El Nino? –The general monthly and seasonal temperature and precipitation conditions –The lack of Atlantic hurricanes –Snowstorms? –An event attributed to El Nino by a NOAA employee speaking in an official capacity

Changnon Losses during El Nino: –Rain in the southeast (including Florida) Unusual tornadoes Crop damage by rain Reduced tourism Direct damage from storms

Changnon Losses during El Nino: –Storms: October, 1997 in Midwest January, 1998 in New England April, 1998 in Ohio Valley

Changnon Losses during El Nino: –Drought in Hawaii –Ski resorts in Midwest –Producers of salt, natural gas, snowmobiles, etc. –Fires in Florida

Changnon Benefits during El Nino: –Mild Winter in Midwest: Few lives lost (13 vs. 757!) Lower fuel costs (10% nationally!) Fewer airline and shipping delays Longer construction season Snow removal costs

Changnon Benefits of El Nino: –No landfalling hurricanes 13 lives, $5 billion, saved

Changnon Benefits of El Nino: –Difficult to quantify: Improvement in lifestyle Recharging reservoirs

Changnon Losses: –Human lives lost: 189 –Economic costs:$4.2 billion Benefits: –Human lives saved: 850 –Economic gains: $19.6 billion

Changnon Lessons: “…the need to focus on both the good and bad impacts of predicted weather conditions. The media tends to focus only on the negative outcomes.”

Changnon Lessons: –“News… writers tend to approach “local” experts for interpretations of the events… [resulting] in widely different interpretations…”

Changnon Lessons: –“…all weather conditions produce winners and losers”

Changnon Lessons: –“…predicting future impacts on lives and the economy due to expected weather is likely as difficult as making accurate long range weather predictions.”